This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. TraI, a protein from the conjugative plasmid F factor, is essential for the plasmid transfer process. The protein includes a relaxase activity that cleaves one plasmid strand prior to transfer, and a helicase activity ---- both of which must be in one polypeptide chain for efficient conjugative transfer. We have determined the crystal structure of the relaxase domain (the N-terminal 36 kDa of the 192 kDa protein), and are near solving the 3D NMR structure of a second 20 kDa region. The C-terminal domain has been solved, and we are pursuing structures of other domains. We want to collect SAXS data to determine the shape of the intact protein and various fragments, and attempt to fit the regions of known structure into the resulting shapes. The experiments will provide information on the orientation of the domains relative to each other and whether the orientation of the domains changes upon DNA binding.